OSHKOSH — Republican presidential hopeful Gov. Scott Walker on Monday banned abortions in Wisconsin after 20 weeks of pregnancy — a law that is sure to curry favor with conservative voters but could be successfully challenged in court.

Wisconsin is the 14th state to pass a ban on abortions at no later than 20 weeks, according to the Guttmacher Institute, which challenges a standard set by the U.S. Supreme Court in the 1973 Roe v. Wade decision that says fetuses are generally considered “viable,” or capable to live outside of the womb, between 24 and 28 weeks of pregnancy.

“I think most people in this state understand that when an unborn child can feel pain, that more than ever is an appropriate time to protect the unborn child,” Walker said at the bill signing at Fox Valley Technical College in Oshkosh, arguing a fetus can feel pain after five months.

However, the American Congress of Obstetricians and Gynecologists and the Journal of the American Medical Association have concluded that evidence shows fetuses begin to feel pain during the third trimester — which begins at 27 weeks.

Bans in some states have been ruled unconstitutional because they ban abortions before the U.S. Supreme Court’s definition of viability.

A U.S. appeals court ruled in May that a 20-week abortion ban in Idaho was unconstitutional because it banned abortions before fetuses are viable, for example.

The same reasoning was used this year to strike down an Arkansas ban on abortions after 12 weeks, however a 20-week ban that has not been challenged in court still exists in Arkansas.

In 2014, a federal judge overturned a North Dakota law banning abortions after six weeks, when a fetal heartbeat can be detected. “A woman’s constitutional right to terminate a pregnancy before viability has been recognized by the United States Supreme Court for more than 40 years,” U.S. District Judge Daniel L. Hovland wrote. “This court is not free to impose its own view of the law.”

The U.S. Supreme Court chose in 2014 not to hear an Arizona case banning abortions after 20 weeks, without providing a reason.

Iris Riis, spokeswoman for Planned Parenthood of Wisconsin, said the group would not have a legal standing to challenge the law because it does not ban services provided by Planned Parenthood. She and others contacted Monday by the State Journal said they were unaware of a lawsuit in the works.

Walker has long been a proponent of anti-abortion legislation, but during his re-election campaign last year he expressed support for leaving pregnancy decisions to women and their doctors. That stance drew criticism from religious conservatives earlier this year.

In March, Walker requested the 20-week abortion ban with no exceptions for rape and incest.

Under the law, doctors who terminate pregnancies after 20 weeks in non-emergency situations could be charged with a felony and face up to three years in prison and a $10,000fine.

Kaylie Hanson, a spokeswoman for the Democratic National Committee, decried Walker’s signing of the bill in a statement.

Hanson said the bill is part of an attempt by Walker to rally the Republican base as he launches his presidential campaign.

“This law doesn’t only undermine the most basic women’s health services. It’s radical, dangerous and lacks respect for half the population of Wisconsin,” Hanson said.

Contact reporter Molly Beck at mbeck@madison.com or 608-252-6135 and Matthew DeFour at mdefour@madison.com or 608-252-6144.

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